Method for transmitting wireless power in wireless charging system including a wireless power transmitting unit and wireless power receiving unit

ABSTRACT

A method for transmitting wireless power in a wireless charging system is provided and includes receiving at least one of information on an available maximum temperature and maximum voltage value information of a back end of a rectification unit from at least one wireless power receiving unit (PRU) from among a plurality of PRUs, receiving at least one of information on a current temperature and current voltage value information of the back end of the rectification unit from each of the plurality of PRUs, and determining a dominant PRU among the plurality of PRUs based on the at least one of information.

PRIORITY

This application claims priority under 35 U.S.C. § 119(a) to KoreanPatent Application Serial Nos. 10-2015-0106039 and 10-2015-0173960,which were filed in the Korean Intellectual Property Office on Jul. 27,2015 and Dec. 8, 2015, respectively, the entire contents of eachapplication is incorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates generally to wireless charging and, moreparticularly, to a method for transmitting wireless power in a wirelesscharging system including a wireless power transmitting unit and awireless power receiving unit.

2. Description of the Related Art

Mobile terminals such as a mobile phone, a personal digital assistant(PDA) and the like are configured for use with rechargeable batteriesdue to their nature, and the battery of the mobile terminal is chargedthrough supplied electronic energy by using a separate chargingapparatus. Typically, the charging device and the battery have separatecontact terminals at an exterior thereof and are electrically connectedto each other by contact between the contact terminals.

However, in such a contact-type charging scheme, the contact terminalsprotrude outwardly, and thus are easily contaminated by foreignsubstances or exposed to moisture. As a result, battery charging may notbe performed correctly.

Recently, wireless charging or non-contact charging technology has beendeveloped and used for electronic devices, e.g., a mobile phone, tosolve the above-mentioned problem.

The wireless charging technology uses wireless power transmission andreception which allows a battery to be automatically charged if thebattery is positioned on a charging pad, i.e., without connecting amobile phone which includes the battery to a separate chargingconnector. The wireless charging technology can improve the portabilityof the electronic devices because it does not require a wired charger.

The wireless charging technology can include an electromagneticinduction scheme which uses a coil, a resonance scheme which usesresonance, and an RF/microwave radiation scheme which convertselectrical energy to a microwave energy and then transmits the microwaveenergy.

It is considered up to now that the electromagnetic induction scheme ismainstream.

A power transmission method through the electromagnetic inductionincludes transmitting electric power between a first coil and a secondcoil. When a magnet is moved in a coil, an induction current occurs. Byusing the induction current, a magnetic field is generated at atransmitting end, and an electric current is induced according to achange in the magnetic field so as to generate energy at a receivingend. The phenomenon is referred to as magnetic induction, and the powertransmission method using magnetic induction has high energytransmission efficiency.

The resonance scheme includes a system in which electricity iswirelessly transferred using an electric power transmission principle ofthe resonance scheme based on a coupled mode theory. It is known thatthe resonant electrical energy does not affect surrounding machines orhuman bodies differently from other electromagnetic waves because theresonant electrical energy is directly transferred only to a devicehaving a resonance frequency and unused parts are reabsorbed into anelectromagnetic field instead of spreading into the air.

In order to sense a state where a wireless power receiving unit (PRU) islocated on a wireless power transmitting unit (PTU), a method fordetecting a change in the impedance of a power transmitter can beprovided.

When the PTU detects the presence of a PRU through the detection ofimpedance change, the PTU may initiate communication with the PRU bysupplying enough power to communicate with the PRU.

On the other hand, in a multi-charging state where one PTU charges aplurality of PRU, when a charging voltage for one PRU is excessivelyhigh or an exothermic reaction occurs, the PTU or PRU may experience afailure or may not charge normally.

SUMMARY

An aspect of the present disclosure provides a method for transmittingwireless power in a wireless charging system, a wireless powertransmitting unit, and a PRU, which can efficiently control charging fora plurality of PRUs by setting a dominant PRU in consideration of a heatgeneration rate of each PRU in a multi-charge situation where one PTUcharges the plurality of PRUs.

An aspect of the present disclosure provides a method for transmittingwireless power in a wireless charging system, a wireless powertransmitting unit, and a PRU, which can efficiently control charging fora plurality of PRUs by setting a dominant PRU in consideration of acharging voltage rate of each PRU in a multi-charge situation where onePTU charges the plurality of PRUs.

In accordance with an aspect of the present disclosure there is provideda method for transmitting wireless power in a wireless charging system.A method for transmitting wireless power in a wireless charging systemis provided and includes receiving at least one of information on anavailable maximum temperature and maximum voltage value information of aback end of a rectification unit from at least one wireless powerreceiving unit (PRU) from among a plurality of PRUs, receiving at leastone of information on a current temperature and current voltage valueinformation of the back end of the rectification unit from each of theplurality of PRUs, and determining a dominant PRU among the plurality ofPRUs based on the at least one of information.

In accordance with an aspect of the present disclosure there is provideda PTU. The PTU includes a communication unit that is configured toreceive at least one of information on an available maximum temperatureand maximum voltage value information of a back end of a rectificationunit and receive at least one of information on a current temperatureand current voltage value information of the back end of therectification unit from at least one wireless power receiving unit (PRU)from among a plurality of PRUs, a processor that is configured todetermine a dominant PRU among the plurality of PRUs based on the atleast one of information, and a power transmitter that is configured totransmit power to the plurality of PRUs based on the control of thecontroller.

In accordance with an aspect of the present disclosure there is provideda PRU The PRU includes a temperature sensor that is configured to sensea temperature, a processor that is configured to generate a signalincluding the available maximum temperature and a signal including thecurrent temperature sensed by the temperature sensor, and acommunication unit configured to transmit the signal including theavailable maximum temperature and the signal including the currenttemperature to the wireless power transmitting unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram of a wireless charging system, according to anembodiment of the present disclosure;

FIG. 2 is a diagram of a PTU and a PRU, according to an embodiment ofthe present disclosure;

FIG. 3 is a diagram of the PTU and the PRU, according to the embodimentof the present disclosure;

FIG. 4 is a signaling diagram of the PTU and the PRU, according to anembodiment of the present disclosure;

FIG. 5 is a flowchart of a method for operating the PTU and the PRU,according to an embodiment of the present disclosure;

FIG. 6 is a graph on a time axis of an amount of power applied by awireless power transmitting unit, according to an embodiment of thepresent disclosure;

FIG. 7 is a flowchart of a control method of the wireless powertransmitting unit, according to an embodiment of the present disclosure;

FIG. 8 is a graph on a time axis of an amount of power applied by thePTU of FIG. 7, according to an embodiment of the present disclosure;

FIG. 9 is a flowchart of a control method of a wireless powertransmitting unit, according to an embodiment of the present disclosure;

FIG. 10 is a graph on a time axis of an amount of power applied by thePTU of FIG. 9, according to an embodiment of the present disclosure;

FIG. 11 is a diagram of a PTU and a PRU in a stand-alone (SA) mode,according to an embodiment of the present disclosure;

FIG. 12 is a flowchart of a processing method of a wireless powertransmitting unit, according to an embodiment of the present disclosure;

FIG. 13 is a flowchart of a processing method of a PRU, according to anembodiment of the present disclosure;

FIG. 14 is a flowchart of a processing method of a wireless powertransmitting unit, according to an embodiment of the present disclosure;and

FIG. 15 is a flowchart of a processing method of a PRU, according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described herein belowwith reference to the accompanying drawings. However, the embodiments ofthe present disclosure are not limited to the specific embodiments andshould be construed as including all modifications, changes, equivalentdevices and methods, and/or alternative embodiments of the presentdisclosure. In the description of the drawings, similar referencenumerals are used for similar elements.

FIG. 1 is a diagram of a wireless charging system, according to anembodiment of the present disclosure. As shown in FIG. 1A, a wirelesscharging system includes a PTU 100 and one or more PRUs 110-1, 110-2, .. . , and 110-n.

The PTU 100 wirelessly transmits electric power 1-1, 1-2, . . . , and1-n to the one or more PRUs 110-1, 110-2, . . . , and 110-n,respectively. Particularly, the PTU 100 may wirelessly transmit electricpower 1-1, 1-2, . . . , and 1-n to only a PRU which is authenticatedthrough a predetermined authentication procedure.

The PTU 100 may achieve an electrical connection with the PRUs 110-1,110-2, . . . , and 110-n. For example, the PTU 100 may transmit wirelesselectric power in the form of electromagnetic waves to the wirelesspower receiving 110-1, 110-2, . . . , and 110-n.

Meanwhile, the PTU 100 may perform bidirectional communication with thePRUs 110-1, 110-2, . . . , and 110-n. Here, the PTU 100 and the PRUs110-1, 110-2, . . . , and 110-n may process packets 2-1, 2-2, . . . ,2-n including a predetermined number of frames, or transmit and receivethe packets. The frames will be described below in more detail below.The PRU may be implemented, for example, in a mobile communicationterminal, a PDA, a portable multimedia player (PMP), a smartphone, andthe like.

The PTU 100 may transmit electric power to the plurality of PRUs 110-1,110-2, . . . , and 110-n through a resonant scheme. When the PTU 100adopts the resonant scheme, the distance between the PTU 100 and theplurality of PRUs 110-1, 110-2, . . . , and 110-n is less than or equalto 30 m. Further, when the PTU 100 adopts the electromagnetic inductionscheme, the distance between the PTU 100 and the plurality of PRUs110-1, 110-2, . . . , and 110-n is less than or equal to 10 cm.

The PRUs 110-1, 110-2, . . . , and 110-n may receive wireless electricpower from the PTU 100 to charge batteries provided in the PRUs 110-1,110-2, . . . , and 110-n. Further, the PRUs 110-1, 110-2, . . . , and110-n may transmit a signal of requesting a wireless power transmission,information necessary for a reception of wireless electric power,information on a status of the PRUs, and/or information on a control ofthe PTU 100 to the PTU 100. Information on the transmitted signal willbe described below in more detail below.

Further, the PRUs 110-1, 110-2, . . . , and 110-n may transmit a messageindicating a charging state of each of the PRUs 110-1, 110-2, . . . ,and 110-n to the PTU 100.

The PTU 100 may include a display device such as a display, and displaya state of each of the PRUs 110-1, 110-2, and 110-n based on the messagereceived from each of the PRUs 110-1, 110-2, . . . , and 110-n. Also,the PTU 100 may display an expected time period until the charging ofeach of the PRUs 110-1, 110-2 and 110-n is completed, together with thestate of each of the PRUs 110-1, 110-2 and 110-n.

The PTU 100 may transmit a control signal for disabling a wirelesscharging function to each of the PRUs 110-1, 110-2, . . . , and 110-n.The PRUs having received the disable control signal of the wirelesscharging function from the PTU 100 may disable the wireless chargingfunction.

FIG. 2 is a diagram of a PTU and a PRU, according to an embodiment ofthe present disclosure.

As illustrated in FIG. 2, the PTU 200 may include a power transmitter211, a controller (or processor) 212, a communication unit 213, adisplay unit 214, and a storage unit 215.

The power transmitter 211 provides power that is required by the PTU200, and wirelessly provide power to the PRU 250. The power transmitter211 may supply power in an alternating current (AC) waveform type, ormay convert power in a direct current (DC) waveform type to the power inthe AC waveform type by using an inverter and supplying the power in theAC waveform type. The power transmitter 211 may be implemented in theform of an embedded battery or in the form of a power receptioninterface so as to receive the power from outside and supply the powerto other elements.

The controller 212 controls the overall operations of the PTU 200 byusing an algorithm, a program, or an application that is required for acontrol, which is read from a storage unit 215. The controller 212 maybe implemented in a form of a central processing unit (CPU), amicroprocessor, or a mini computer.

The communication unit 213 communicates with the PRU 250, and mayreceive power information from the PRU 250. Here, the power informationmay include at least one of a capacity of the PRU 250, a residual amountof the battery, a number of charging times, an amount of use, a batterycapacity, and a proportion of the battery.

Further, the communication unit 213 transmits a signal of controlling acharging function in order to control the charging function of the PRU250. The signal of controlling the charging function may be a controlsignal of controlling the power receiver 251 of the specific PRU 250 soas to make the charging function to be enabled or disabled. Morespecifically, the power information may include information on aninsertion of a wire charging terminal, a transition from a stand-alone(SA) mode to a non-SA (NSA) mode, error state release and the like.

In addition, the charging function control signal may includeinformation associated with power adjustment or a power control commandto address the occurrence of an abnormal situation according to variousembodiments of the present disclosure.

The communication unit 213 receives a signal from another wireless powertransmitter as well as the PRU 250. For example, the communication unit213 may proceed with a registration procedure for wireless charging byreceiving an advertisement signal transmitted from a communication unit253 of the PRU 250.

The controller 212 displays a state of the PRU 250 on the display unit214 based on the message received from the PRU 250 through thecommunication unit 213. Further, the controller 212 may display, on thedisplay 214, an expected time period until the charging of the PRU 250is completed.

Furthermore, as illustrated in FIG. 2, the PRU 250 may include at leastone of the power receiver 251, the controller 252, the communicationunit 253, a display unit 258, and a storage unit 259.

The power receiver 251 may wirelessly receive power transmitted from thePTU 200. Here, the power receiving unit 251 may receive power in an ACwaveform.

The controller (or processor) 252 may control the overall operations ofthe PRU 250 by using an algorithm, a program, or an application requiredfor a control, which is read from a storage unit. The controller 252 maybe implemented in a form of a central processing unit (CPU), amicroprocessor, or a mini computer.

The communication unit 253 communicates with the PTU 200 through apredetermined scheme. The communication unit 253 may transmit powerinformation to the PTU 200. Here, the power information may include atleast one of a capacity of the PRU 250, a residual amount of thebattery, a number of charging times, an amount of use, a batterycapacity, and a proportion of the battery.

Further, the communication unit 253 may transmit a signal forcontrolling a charging function in order to control the chargingfunction of the PRU 250. The signal for controlling the chargingfunction may be a control signal for controlling the power receiver 251of the specific PRU 250 so as to enable or disable the chargingfunction. More specifically, the power information may includeinformation on an insertion of a wire charging terminal, a transitionfrom a SA mode to a NSA mode, error state release and the like. Inaddition, the charging function control signal may include informationassociated with power adjustment or a power control command to addressthe occurrence of an abnormal situation.

In addition, the communication unit 253 may proceed with theregistration procedure for wireless charging by receiving a beaconsignal transmitted from the power transmitter 211 of the PTU 200 throughthe power receiver 251, and then transmitting an advertisement signal tothe PTU 200 within a predetermined time.

The controller 252 may control a state of the PRU 250 to be displayed onthe display unit 258. Further, the controller 252 may also display, onthe display unit 258, an expected time period until the PRU 250 iscompletely charged.

FIG. 3 is a diagram of a PTU and a PRU, according to the embodiment ofthe present disclosure.

As shown in FIG. 3, the PTU 200 includes at least one of a transmittingside resonator (Tx resonator) 211 a, the controller 212 (for example, anMCU (Microcontroller), the communication unit 213 (for example, anout-of-band signaling unit), a matching unit 216, a driver 217, anamplifier (power amp) 218, or a sensing unit 219. The PRU 250 mayinclude at least one of a receiving side resonator (Rx resonator) 251 a,the controller 252, a control circuit unit 252 a, the communication unit253, a rectifier 254, a DC/DC converter 255, a switching unit 256, orloading unit (client device load) 257.

The driver 217 outputs DC power having a preset voltage value. Thevoltage value of the DC power output from the driver 217 may becontrolled by the controller 212.

The DC power output from the driver 217 may be output to the amplifier218. The amplifier 218 may amplify the DC power by a preset gain.Further, the DC power may be converted into AC power based on a signalinput from the controller 212. Accordingly, the amplifier 218 may outputAC power.

The matching circuit 216 performs impedance matching. For example, theoutput power may be controlled to have high efficiency or high capacityby adjusting the impedance viewed from the matching circuit 216. Thesensing unit 219 may sense a load change caused by the PRU 250 throughthe Tx resonator 211 a or the amplifier 218. The sensing result of thesensing unit 219 may be provided in the controller 212.

When the PTU 200 transmits a short beacon signal or a long beacon signalto the PRU 250, the PRU 250 may generate a load change by a pre-setcircuit or the like. The sensing unit 219 of the PTU 200 may detect theload change in the PRU 250, and may provide a result of detecting theload change to the controller 212. The controller 212 may detect thepresence of PRU 250 based on the load change detected by the sensingunit 219, or may extend or adjust the transmission period of the beaconsignal (e.g., long beacon signal).

The matching circuit 216 may adjust the impedance based on a control ofthe controller 212. The matching unit 216 may include at least one of acoil and a capacitor. The controller 212 may control a connection statewith at least one of the coil and the capacitor and may, accordingly,perform the impedance matching.

The Tx resonator 211 a may transmit the input AC power to the Rxresonator 251 a. The Tx resonator 211 a and the Rx resonator 251 a maybe implemented in a resonant circuit having the same resonancefrequency. For example, the resonance frequency may be determined as6.78 MHz.

Meanwhile, the communication unit 213 may communicate with thecommunication unit 253 of the PRU 250, and perform communication(wireless-fidelity (Wi-Fi™), ZigBee™, or Bluetooth™ (BT)/Bluetooth lowenergy (BLE)) with, for example, a bi-directional 2.4 GHz frequency.

The Rx resonator 251 a may receive power for charging. In addition, theRx resonator 251 a may receive the beacon signal (e.g., short beaconsignal or long beacon signal, etc.) transmitted through the Tx resonator211 a of the PTU 200.

The rectifier 254 may rectify wireless power received by the Rxresonator 251 a in the DC form, and may be implemented in, for example,the form of a bridge diode. The DC/DC converter 255 may convert therectified electric current into a predetermined gain. For example, theDC/DC converter 255 may convert the rectified power in such a mannerthat the output side thereof has a voltage of 5V. On the other hand, theminimum and maximum values of a voltage, which can be applied to a frontend of the DC/DC converter 255, may be set in advance.

The switch 256 connects the DC/DC converter 255 to the loading unit 257.The switch 256 is held in an on/off state under a control of thecontroller 252. In some embodiments, the switch 256 may be omitted. In acase where the switch 256 is in the on state, the loading unit 257 maystore converted electric power which is input from the DC/DC converter255.

The control circuit unit 252 a may generate a control signal forcontrolling the switch unit 256 by a signal received through the Rxresonator 251 a of the PRU 250. For example, the control circuit unit252 a, separate from the controller 252, is driven by the signal (forexample, the short beacon signal or the long beacon signal) received bythe PRU 250 so as to control the switch 256 to generate the load change.The control circuit unit 252 a can also generate the load change in thePRU 250 when power is not supplied to the controller 252 or without theoperation of the controller 252.

Further, the control circuit unit 252 a may generate a code or a signalhaving a predetermined pattern by the signal (e.g., the short beaconsignal or long beacon signal) received through the Rx resonator 251 a ofthe PRU 250. The control circuit unit 252 a may control the switch 256by the generated code or signal, and accordingly generate a load changecorresponding to the predetermined code or signal. The PTU 200 mayacquire predetermined information (for example, information related toextension of the period of the beacon signal, etc.) by detecting theload change of the wireless power receiver 250 and decoding thepredetermined code or signal.

FIG. 4 is a signaling diagram of a PTU and a PRU, according to anembodiment of the present disclosure. As shown in FIG. 4, a PTU 400 mayapply electric power in step S401. When the power is applied, the PTU400 may configure an environment in step S402.

The PTU 400 may enter a power saving mode in step S403. In the powersaving mode, the PTU 400 may apply different power beacons for detectionin their own cycles, a detailed description thereof will be made withreference to FIG. 6. For example, as illustrated in FIG. 4, the PTU 400may apply power beacons for detection (e.g., the short beacon signal orlong beacon signal) in steps S404 and S405, and the power beacons fordetection may be different from each other in terms of the power value.A part or all of the detection power beacons may have enough power todrive the communication unit of the PRU 450. For example, the PRU 450may drive the communication unit by the part or all of the detectionpower beacons to communicate with the PTU 400. Here, the above state maybe named a null state, which is indicated at step 406.

The PTU 400 may detect a load change by an arrangement of the PRU 450.The PTU 400 may enter a low power mode in step S408. The low power modewill also be described in more detail with reference to FIG. 6.Meanwhile, the PRU 450 may drive the communication unit based on powerreceived from the PTU 400 in step S409.

The wireless power receiver 450 may transmit a PTU searching signal tothe PTU 400 in step S410. The PRU 450 may transmit the PTU searchingsignal as an advertisement (AD) signal using BLE. The PRU 450 maytransmit the PTU searching signal periodically or until a preset timearrives and may receive a response signal from the PTU 400.

When receiving the PTU searching signal from the PRU 450, the PTU 400may transmit a PRU response signal in step S411. Here, the PRU responsesignal may establish a connection between the PTU 400 and the PRU 450.

The PRU 450 may transmit a PRU static signal in step S412. Here, the PRUstatic signal may be a signal indicating a state of the PRU 450, and maybe used to request subscription to a wireless power network managed bythe PTU 400.

The PTU 400 may transmit a PTU static signal in step S413. The PTUstatic signal transmitted by the PTU 400 may be a signal indicatingcapability of the PTU 400.

When the PTU 400 and PRU 450 transmit and receive the PRU static signaland PTU static signal, the PRU 450 may periodically transmit a PRUdynamic signal, in steps S414 and S415. The PRU dynamic signal mayinclude information on at least one parameter measured by the PRU 450.For example, the PRU dynamic signal may include information on a voltageat a back end of the rectifier of the PRU 450. The status of the PRU 450may be referred to as a boot status, which is referenced by S407.

The PTU 400 may enter a power transmission mode in step S416, and thePTU 400 may transmit a PRU control signal that is a command signal whichenables the PRU 450 to perform the charging in step S417. In the powertransmission mode, the PTU 400 may transmit charging power.

The PRU control signal transmitted by the PTU 400 may includeinformation enabling/disabling the charging of the PRU 450 andpermission information. The PRU control signal may be transmittedwhenever a charging state is changed. The PRU control signal may betransmitted, for example, every 250 ms, or transmitted when a parameteris changed. The PRU control signal may be set to be transmitted within apreset threshold, for example, within one second even though theparameter is not changed.

The PRU 450 may change a configuration according to the PRU controlsignal and transmit the PRU dynamic signal for reporting the state ofthe PRU 450 in steps S418 and S419. The PRU dynamic signal transmittedby the PRU 450 may include at least one of voltage information, currentinformation, information on a state of the PRU, and temperatureinformation. The state of the PRU 450 may be called an on state, whichis referenced by S421.

Meanwhile, the PRU dynamic signal may have a data structure as indicatedin Table 1.

TABLE 1 Field Octets Description Use Units Optional fields validity 1Defines which optional fields are Mandatory populated V_(RECT) 2 Voltageat diode output Mandatory mV I_(RECT) 2 Current at diode outputMandatory mA V_(OUT) 2 Voltage at charge/battery port Optional mVI_(OUT) 2 Current at charge/battery port Optional mA Temperature 1Temperature of PRU Optional Degrees Celsius (from −40° C.) V_(RECT) _(—)_(MIN) _(—) _(DYN) 2 V_(RECT) _(—) _(LOW) _(—) _(LIMIT) Optional mV(dynamic value) V_(RECT) _(—) _(SET) _(—) _(DYN) 2 Desired V_(RECT)Optional mV (dynamic value) V_(RECT) _(—) _(HIGH) _(—) _(DYN) 2 V_(RECT)_(—) _(HIGH) _(—) _(LIMIT) Optional mV (dynamic value) PRU alert 1Warnings Mandatory Bit field RFU 3 Undefined

As shown in Table 1, the PRU dynamic signal may include one or morefields that may be configured to include optional field information,information on a voltage at the back end of the rectifier of the PRU,information on current at the back end of the rectifier of the PRU,information on a voltage at the back end of the DC/DC converter of thePRU, information on current at the back end of the DC/DC converter ofthe PRU, temperature information, information on the minimum voltagevalue (V_(RECT) _(_) _(MIN) _(_) _(DYN)) at the back end of therectifier of the PRU, information on an optimum voltage value (V_(RECT)_(_) _(SET) _(_) _(DYN)) at the back end of the rectifier of the PRU,maximum voltage value (V_(RECT) _(_) _(HIGH) _(_) _(DYN)) information ofthe back end of the rectifier of the PRU, and warning information (PRUalert). The PRU dynamic signal may include at least one of the abovefields.

For example, one or more voltage setting values (for example, theminimum voltage value information (V_(RECT) _(_) _(MIN) _(_) _(DYN)) ofthe back end of the rectifier of the PRU, the optimal voltage valueinformation (V_(RECT) _(_) _(SET) _(_) _(DYN)) of the back end of therectifier of the PRU, and the maximum voltage value (V_(RECT) _(_)_(HIGH) _(_) _(DYN)) information of the back end of the rectifier of thePRU) determined according to a charging state may be inserted intocorresponding fields of the PRU dynamic signal and then transmitted. Assuch, the PTU that has received the PRU dynamic signal may adjust awireless charging voltage to be transmitted to each PRU, with referenceto the voltage setting values included in the PRU dynamic signal.

The alert information (PRU Alert) may have a data structure shown inTable 2 below.

TABLE 2 7 6 5 4 3 2 1 0 Over-voltage Over-current Over-temp ChargeComplete TA detect Transition restart RFU request

Referring to Table 2, the alert information (PRU Alert) may include abit for a restart request, a bit for a transition, and a bit fordetecting an insertion of a travel adapter (TA detect). The TA detectindicates a bit informing of a connection between the PTU providingwireless charging and a terminal for wired charging by the PRU. The bitfor the transition indicates a bit informing the PTU that the PRU isreset before a communication integrated circuit (IC) of the PRU isswitched from a SA mode to a NSA mode. The restart request indicates abit informing the PRU that the PTU is ready to restart the charging whenthe charging is disconnected since the PTU reduces power due to thegeneration of an over current state or an over temperature state andthen the state is returned to the original state.

Further, the alert information (PRU Alert) may also have a datastructure shown in Table 3 below.

TABLE 3 7 6 5 4 3 2 1 0 PRU Over-Voltage PRU Over- PRU Over- PRU SelfCharge Wired Mode Mode Current Temperature Protection Complete ChargerTransition Transition Detect Bit 1 Bit 0

Referring to Table 3 above, the alert information may include overvoltage, over current, over temperature, PRU self-protection, chargecompete, wired charger detect, mode transition and the like. When theover voltage field is set as “1”, it may indicate that a voltage Vrectof the PRU exceeds a limit of the over voltage. Further, the overcurrent and the over temperature may be set in the same way as the overvoltage. In addition, the PRU self-protection indicates that the PRUdirectly reduces a load of power and thus protects itself. In thisevent, the PTU is not required to change a charging state.

Bits for a mode transition may be set as a value informing the PTU of aperiod during which a mode transition process is performed. The bitsindicating the mode transition period may be expressed as shown in Table4 below.

TABLE 4 Value (Bit) Mode Transition Bit Description 00 No ModeTransition 01 2 s Mode Transition time limit 10 3 s Mode Transition timelimit 11 6 s Mode Transition time limit

Referring to Table 4 above, “00” indicates that there is no modetransition, “01” indicates that a time required for completing the modetransition is a maximum of two seconds, “10” indicates that a timerequired for completing the mode transition is a maximum of threeseconds, and “11” indicates that a time required for completing the modetransition is a maximum of six seconds.

For example, when three seconds or less are spent for completing themode transition, the mode transition bit may be set as “10”. Prior tostarting the mode transition process, the PRU may make a restrictionsuch that there is no change in impedance during the mode transitionprocess by changing an input impedance setting to match 1.1 W powerdraw. Accordingly, the PTU may adjust power (I_(TX) _(_) _(COIL)) forthe PRU in accordance with the setting, and accordingly, maintain thepower (I_(TX) _(_) _(COIL)) for the PRU during the mode transitionperiod.

Accordingly, when the mode transition period is set by the modetransition bit, the PTU may maintain the power (I_(TX) _(_) _(COIL)) forthe PRU during the mode transition time, for example, three seconds.That is, the PTU may maintain a connection even though a response is notreceived from the PRU for three seconds. However, after the modetransition time passes, the PRU may be considered as a rogue object andthus power transmission may be terminated.

Meanwhile, the PRU 450 may detect the generation of errors. The PRU 450may transmit an alert signal to the PTU 200 in step S420. The alertsignal may be transmitted in the form of the PRU dynamic signal or a PRUalert signal. For example, the PRU 450 may transmit the PRU alert fieldof Table 1 reflecting an error state to the PTU 400. Alternatively, thePRU 450 may transmit a single alert signal indicating the error state tothe PTU 400. When receiving the alert signal, the PTU 400 may enter alatch fault mode in step S422. The PRU 450 may enter a null state instep S423.

FIG. 5 is a flowchart of a method for operating a PTU and a PRU,according to an embodiment of the present disclosure. The process ofFIG. 5 will be described in more detail with reference to FIG. 6 below.FIG. 6 is a graph on a time axis (x axis) of an amount of power appliedby a PTU of FIG. 5, according to an embodiment of present disclosure.

As illustrated in FIG. 5, the PTU may initiate the method in step S501.Further, the PTU may reset an initial configuration in step S503. ThePTU may enter a power saving mode in step S505. Here, the power savingmode may be an interval where the PTU applies power having differentamounts to the power transmitter. For example, the power saving mode maycorrespond to an interval where the PTU applies second detection power601 and 602 and third detection power 611, 612, 613, 614, and 615 to thepower transmitter in FIG. 6. Here, the PTU may periodically apply thesecond detection power 601 and 602 by second period. When the PTUapplies the second detection power 601 and 602, the application maycontinue for a second term. The PTU may periodically apply the thirddetection power 611, 612, 613, 614, and 615 by third period. When thePTU applies the third detection power 611, 612, 613, 614, and 615, theapplication may continue for a third term. Meanwhile, although it isillustrated that power values of the third detection power 611, 612,613, 614, and 615 are different from each other, the power values of thethird detection power 611, 612, 613, 614, and 615 may be different orthey may be the same.

The PTU may output the third detection power 611 and then output thethird detection power 612 having the same size of the power amount. Asdescribed above, when the PTU outputs the third detection power havingthe same magnitude, the power amount of the third detection power may bea sufficient amount to detect a minimal sized PRU, e.g., a PRU of acategory (a type of PRU) 1.

On the other hand, the PTU may output the third detection power 611 andthen output the third detection power 612 having a different size of thepower amount. When the PTU outputs the third detection power having thedifferent amount as described above, the amount of the third detectionpower may be a sufficient amount to detect a PRU of categories 1 to 5.For example, when the third detection power 611 may have a power amountby which a PRU of category 5 can be detected, the third detection power612 may have a power amount by which a PRU of category 3 can bedetected, and the third detection power 613 may have a power amount bywhich a PRU of category 1 can be detected.

Meanwhile, the second detection power 601 and 602 may be power that candrive the PRU. More specifically, the second detection power 601 and 602may have a power amount that can drive the controller and thecommunication unit of the PRU.

The PTU applies the second detection power 601 and 602 and the thirddetection power 611, 612, 613, 614, and 615 to the power receiver by asecond period and a third period, respectively. When the PRU is disposedon the wireless power transmitting unit, impedance at a point of the PTUmay be changed. For example, the PTU may detect a change in impedancewhile the second detection power 601 and 602 and third detection power611, 612, 613, 614, and 615 are applied. For example, the PTU may detectthe impedance change while the third detection power 615 is applied.Accordingly, the PTU may detect an object in step S507. When the objectis not detected (No in step S507), the PTU may maintain a power savingmode in which different power is periodically applied, in step S505.

Meanwhile, when there is the change in the impedance and thus the objectis detected (Yes in step S507), the PTU may enter a low power mode.Here, the low power mode is a mode in which the PTU applies drivingpower having a power amount by which the controller and thecommunication unit of the PRU can be driven. For example, in FIG. 6, thePTU may apply driving power 620 to the power transmitter. The PRU mayreceive the driving power 620 to drive the controller and/or thecommunication unit. The PRU may perform communication with the PTUaccording to a predetermined scheme based on the driving power 620. Forexample, the PRU may transmit/receive data required for authentication,and may subscribe to the wireless power network, which the PTU manages,on the basis of the transmission/reception of the data. However, when arogue object is arranged instead of the PRU, the datatransmission/reception cannot be performed. Accordingly, the PTU maydetermine whether the arranged object is the rogue object in step S511.For example, when the PTU does not receive a response from the objectwithin a preset time, the PTU may determine the object as the rogueobject.

If it is determined that the object is the rogue object (Yes in stepS511), the PTU may enter the latch fault mode in step S513. If it isdetermined that the object is not the rogue object (No in step S511),however, an entering or subscribing step may be performed in step S519.For example, the PTU may periodically apply first power 631 to 634 by afirst period in FIG. 6. The PTU may detect a change in impedance whileapplying the first power. For example, when the rogue object iswithdrawn (Yes in step S515), the change in the impedance may bedetected and the PTU may determine that the rogue object is withdrawn.Alternatively, when the rogue object is not withdrawn (No in step S515),the PTU may not detect the change in the impedance. When the rogueobject is not withdrawn, the PTU may output at least one of a lamp (orother visual indication) and a warning sound to inform a user that astate of the PTU is an error state. Accordingly, the PTU may include anoutput unit that outputs at least one of the lamp and the warning sound.

When it is determined that the rogue object is not withdrawn (No in stepS515), the wireless power transmitter may maintain the latch fault modein step S513. On the other hand, when it is determined that the objectis withdrawn (Yes in step S515), the PTU may enter the power saving modeagain in step S517. For example, the PTU may apply second power 651 to652 and third power 661 and 665 of FIG. 6.

As described above, when the rogue object is arranged instead of thePRU, the PTU may enter the latch fault mode. In addition, the PTU maydetermine whether the rogue object is withdrawn, according to the changein the impedance based on the power applied in the latch fault mode.That is, a condition of the entrance into the latch fault mode in theembodiment of FIGS. 5 and 6 may be caused by the rogue object.Meanwhile, the PTU may have various latch fault mode entrance conditionsas well as the arrangement of the rogue object. For example, the PTU maybe cross-connected with the arranged PRU and may enter the latch faultmode in the above case.

Accordingly, when the cross-connection is generated, the PTU may berequired to return to an initial state and the PRU may be withdrawn. ThePTU may set the cross-connection, in which the PRU arranged on anotherPTU enters the wireless power network, as a condition of entry into thelatch fault mode. An operation of the PTU when the error is generated,which includes the cross-connection, will be described with reference toFIG. 7.

FIG. 7 is a flowchart of a method of controlling a wireless powertransmitting unit, according to an embodiment of the present disclosure.The method of FIG. 7 will be described in more detail with reference toFIG. 8. FIG. 8 is a graph on a time axis (x axis) of an amount of powerapplied by a PTU of FIG. 7, according to an embodiment of the presentdisclosure.

The PTU may initiate the method in step S701. Further, the PTU may resetan initial configuration in step S703. The PTU may enter the powersaving mode again in step S705. Here, the power saving mode may be aninterval where the PTU applies power having different amounts to thepower transmitter. For example, the power saving mode may correspond toan interval where the PTU applies second detection power 801 and 802 andthird detection power 811, 812, 813, 814, and 815 to the powertransmitter in FIG. 8. Here, the PTU may periodically apply the secondpower 801 and 802 by second period. When the PTU applies the secondpower 801 and 802, the application may continue for a second term. ThePTU may periodically apply the third detection power 811, 812, 813, 814,and 815 by a third period. When the PTU applies the third detectionpower 811, 812, 813, 814, and 815, the application may continue for athird term. Meanwhile, although it is illustrated that power values ofthe third detection power 811, 812, 813, 814, and 815 are different fromeach other, the power values of the third detection power 811, 812, 813,814, and 815 may be different or they may be the same.

Meanwhile, the second detection power 801 and 802 may be power that candrive the PRU. More specifically, the second detection power 801 and 802may have a power amount which can drive the controller and thecommunication unit of the PRU.

The PTU applies the second detection power 801 and 802 and the thirddetection power 811, 812, 813, 814, and 815 to the power receiver by asecond period and a third period, respectively. When the PRU is disposedon the wireless power transmitting unit, impedance at a point of the PTUmay be changed. For example, the PTU may detect a change in impedancewhile the second detection power 801 and 802 and third detection power811, 812, 813, 814, and 815 are applied. For example, the PTU may detectthe impedance change while the third detection power 815 is applied.Accordingly, the PTU may detect an object in step S707. When the objectis not detected (No in step S707), the PTU may maintain the power savingmode in which different power is periodically applied in step S705.

Meanwhile, when the impedance is changed and thus the object is detected(Yes in step S707), the PTU may enter the low power mode in step S709.Here, the low power mode is a mode in which the PTU applies drivingpower having a power amount by which the controller and thecommunication unit of the PRU can be driven. For example, in FIG. 8, thePTU may apply driving power 820 to the power transmitter. The PRU mayreceive the driving power 820 to drive the controller and thecommunication unit. The PRU may perform communication with the PTUaccording to a predetermined scheme based on the driving power 820. Forexample, the PRU may transmit/receive data required for authentication,and may subscribe to the wireless power network, which the wirelesspower transmitter manages, on the basis of the transmission/reception ofthe data.

Thereafter, the PTU may enter the power transmission mode in whichcharging power is transmitted in step S711. For example, the PTU mayapply charging power 821 and the charging power may be transmitted tothe PRU as illustrated in FIG. 8.

The PTU may determine whether an error is generated in the powertransmission mode. Here, the error may be caused by the rogue object onthe wireless power transmitting unit, the cross-connection, overvoltage, over current, over temperature, and the like. The PTU mayinclude a sensing unit that may measure the over voltage, the overcurrent, over temperature, and the like. For example, the PTU maymeasure a voltage or a current at a reference position. When themeasured voltage or current is larger than a threshold, it is determinedthat conditions of the over voltage or the over current are satisfied.Alternatively, the PTU may include a temperature sensing means and thetemperature sensing means may measure temperature at a referenceposition of the wireless power transmitting unit. When temperature atthe reference position is larger than a threshold, the PTU may determinethat a condition of the over temperature is satisfied.

Meanwhile, when an over voltage, over current, or over temperature stateis determined according to a measurement value of the temperature,voltage, or current, the PTU prevents the over voltage, over current, orover temperature by reducing the wireless charging power by a presetvalue. At this time, when a voltage value of the reduced wirelesscharging power is smaller than a preset minimum value (for example, theminimum voltage value (V_(RECT) _(_) _(MIN) _(_) _(DYN)) of the back endof the rectifier of the PRU), the wireless charging is stopped, so thatthe voltage setting value may be re-controlled.

Although it has been illustrated that the error is generated since therogue object is arranged on the PTU in the embodiment of FIG. 8, theerror is not limited thereto and it will be easily understood by thoseskilled in the art that the PTU operates through a similar process withrespect to the rogue object, the cross-connection, the over voltage, theover current, and the over temperature.

When the error is not generated (No in step S713), the PTU may maintainthe power transmission mode in step S711. Meanwhile, when the error isgenerated (Yes in step S713), the PTU may enter the latch fault mode instep S715. For example, the PTU may apply first power 831 to 835 asillustrated in FIG. 8. Further, the PTU may output an error generationdisplay including at least one of a lamp (or other visual indication)and a warning sound during the latch fault mode. When it is determinedthat the rogue object or PRU is not withdrawn (No in step S717), the PTUmay maintain the latch fault mode in step S715. Meanwhile, when it isdetermined that the rogue object or PRU is withdrawn (Yes in step S717),the PTU may enter the power saving mode again in step S719. For example,the PTU may apply second power 851 and 852 and third power 861 to 865 ofFIG. 8.

In the above description, the error is generated while the PTU transmitsthe charging power. Hereinafter, an operation of the PTU when aplurality of PRU receives charging power from the PTU will be described.

FIG. 9 is a flowchart of a method of controlling a wireless powertransmitting unit, according to an embodiment of the present disclosure.The process of FIG. 9 will be described in more detail with reference toFIG. 10. FIG. 10 is a graph on a time axis (x axis) of an amount ofpower applied by a PTU of FIG. 9, according to an embodiment of thepresent disclosure.

As illustrated in FIG. 9, the PTU may transmit charging power to a firstPRU (RX1) in step S901. Further, the PTU may allow a second PRU (RX2) toadditionally subscribe to the wireless power network in step S903. ThePTU may transmit charging power to the second PRU in step S905. Morespecifically, the PTU may apply a sum of the charging power required bythe first PRU and the second PRU to the power receiver.

For example, with reference to FIG. 10, the PTU may maintain the powersaving mode in which second detection power 1001 and 1002 and thirddetection power 1011 to 1015 are applied. Thereafter, the PTU may detectthe first PRU and enter the low power mode in which the detection power1020 is maintained. Next, the PTU may enter the power transmission modein which first charging power 1030 is applied. The PTU may detect thesecond PRU and allow the second PRU to subscribe to the wireless powernetwork. Further, the PTU may apply second charging power 1040 having apower amount corresponding to a sum of power amounts required by thefirst PRU and the second PRU.

Referring back to FIG. 9, the PTU may detect error generation in stepS907 while charging power is transmitted to both the first and secondPRUs in step S905. As described above, the error may be caused by therogue object, the cross-connection, the over voltage, the over current,the over temperature and the like. When the error is not generated (Noin step S907), the PTU may maintain the applying of the second chargingpower 1040.

Meanwhile, when the error is generated (Yes in step S907), the PTU mayenter the latch fault mode in step S909. For example, the PTU may applythe first power 1051, 1052, 1053, 1054, and 1055 of FIG. 10 by a firstperiod. The PTU may determine whether both the first PRU and the secondPRU are withdrawn in step S911. For example, the PTU may detect animpedance change while applying the first power 1051 to 1055. The PTUmay determine whether both the first PRU and the second PRU arewithdrawn based on whether the impedance is returned to an initialvalue.

When it is determined that both the first PRU and the second PRU arewithdrawn (Yes in step S911), the PRU may enter the power saving mode instep S913. For example, the PTU may apply second detection power 1061and 1062 and third detection power 1071 to 1075 by a second period and athird period, respectively.

As described above, even if the PTU applies charging power to aplurality of PRU, the PTU may determine whether the PRU or the rogueobject is withdrawn when the error occurs.

FIG. 11 is a diagram of a PTU and a PRU in a SA mode, according to anembodiment of the present disclosure.

A PTU 1100 includes a communication unit 1110, a PA 1120, and aresonator 1130. The PRU 1150 may include a communication unit 1151, anapplication processor (AP) 1152, a power management integrated circuit(PMIC) 1153, a wireless power integrated circuit (WPIC) 1154, aresonator 1155, an interface power management (IFPM) IC 1157, a TA 1158,and a battery 1159.

The communication unit 1110 of the PTU 1100 may be implemented byWi-Fi/BT Combo IC and communicates with the communication unit 1151 ofthe PRU 1150 in a predetermined scheme, for example, a BLE scheme. Forexample, the communication unit 1151 of the PRU 1150 may transmit thePRU dynamic signal having the data configuration of Table 1 to thecommunication unit 1110 of the PTU 1100. As described above, the PRUdynamic signal may include at least one of voltage information, currentinformation, temperature information and alert information of the PRU1150.

A value of the power output from the power amplifier 1120 may beadjusted based on the received PRU dynamic signal. For example, when theovervoltage, the overcurrent, and the over-temperature are applied tothe PRU 1150, a power value output from the power amplifier 1120 may bereduced. Further, when a voltage or current of the PRU 1150 is smallerthan a preset value, a power value output from the power amplifier 1120may be increased.

Charging power from the resonator 1130 of the PTU 1100 may be wirelesslytransmitted to the resonator 1155 of the PRU 1150.

The WPIC 1154 may rectify the charging power received from the resonator1155 and perform DC/DC conversion. The WPIC 1154 may drive thecommunication unit 1151 or charge the battery 1159 by using theconverted power.

Meanwhile, a wired charging terminal may be inserted into the TA 1158.The TA 1158 may have the wired charging terminal such as a 30 pinconnector or USB connector, and may receive the power supplied from anexternal power source to charge the battery 1159.

The IFPM 1157 may process power applied from the wired charging terminaland output the processed power to the battery 1159 and the PMIC 1153.

The PMIC 1153 may manage wirelessly received power, power receivedthrough a wire, and power applied to each of the components of the PRU1150. The AP 1152 may receive information on the power from the PMIC1153, and may control the communication unit 1151 to transmit the PRUdynamic signal of reporting the power information.

The TA 1158 may be connected to anode 1156 connected to the WPIC 1154.When the wired charging connector is inserted into the travel adapter1158, a predetermined voltage (e.g., a voltage of 5V) may be applied tothe node 1156. The WPIC 1154 may monitor the voltage applied to the node1156 to determine whether the travel adapter is inserted.

The AP 1152 has a stack in a predetermined communication scheme, forexample, a Wi-Fi/BT/BLE stack. Accordingly, in communication for thewireless charging, the communication unit 1151 may load the stack fromthe AP 1152 and may then communicate with the communication unit 1110 ofthe PTU 1100 by using a BT or BLE communication scheme based on thestack.

However, a state may occur in which data for performing wireless powertransmission cannot be fetched from the AP 1152, e.g., the AP 1152 isturned off or in which power is lost so that the AP 1152 cannot remainin an on state while the data is being fetched from a memory within theAP 1152.

When a residual capacity of the battery 1159 is less than a minimumpower threshold, the AP 1152 is turned off, and the wireless chargingcan be performed using some components for the wireless charging,disposed within the PRU, for example, the communication unit 1151, theWPIC 1154, and the resonator 1155. A state where the AP 1152 cannot beturned on may be referred to as a dead battery state.

Since the AP 1152 is not driven in the dead battery state, thecommunication unit 1151 cannot receive a stack in a predeterminedcommunication scheme, for example, a Wi-Fi/BT/BLE stack from the AP1152. For such a case, some of the stacks in the predeterminedcommunication scheme, for example, the BLE stack, are fetched within thememory 1162 of the communication unit 1151 from the AP 1152 and storedin the memory 1162. Accordingly, the communication unit 1151 maycommunicate with the PTU 1100 for the wireless charging by using thestack in the communication scheme stored in the memory 1162, that is, awireless charging protocol. At this time, the communication unit 1151may include a memory, and the BLE stack may be stored in a memory in aform of a read only memory (ROM) in the SA mode.

As described above, a mode in which the communication unit 1151 performsthe communication by using the stack of the communication scheme storedin the memory 1162 may be the SA mode. Accordingly, the communicationunit 1151 manages a charging process based on the BLE stack.

The concept of the wireless charging system which can be applied to thepresent disclosure has been described with reference to FIGS. 1 to 11.Hereinafter, with reference to FIGS. 12 to 15, a method for transmittingwireless power in a wireless charging system, a wireless powertransmitting unit, and a PRU, according to an embodiment of the presentdisclosure will now be described.

The following methods can be used for determining a reference PRU(hereinafter a dominant PRU) in transmitting, by one wireless powertransmitting unit, charging power to a plurality of PRUs.

For example, when transmitting the charging power to one PRU by onewireless power transmitting unit, an optimum charging state for thecorresponding PRU can be maintained by power tracking of V_(RECT) _(_)_(MIN) _(_) _(ERROR). However, when simultaneously charging a pluralityof PRUs by one wireless power transmitting unit, the charging power canbe efficiently controlled by setting or determining the dominant PRU.

As a method for determining the dominant PRU, a highest percentageutilization method is described. The method provides a relativelyefficient way of transmitting power from a wireless transmitting unit toa wireless receiving unit. However, the method may not efficientlyoperate for a plurality of PRUs having different temperature settings ordissipation. For example, the dominant PRU determined by the method maynot be an optimum dominant PRU, and the temperature of another PRU mayincrease above a threshold temperature while the dominant PRU is beingcharged.

For example, the temperature of the PRU may be an important factor indetermining the dominant PRU. Accordingly, a dominant PRU may be set ordetermined by considering the temperature of the PRU.

In addition, a difference of coupling efficiency of the resonator maygenerate a difference of V_(RECT) in each PRU. Some PRUs may have highefficiency and have a large margin because V_(RECT) is lower thanV_(RECT) _(_) _(HIGH), and V_(RECT) of any PRU may not have a margin.Since V_(RECT) may vary in a combination of a PRU and a wireless powertransmitting unit, V_(RECT) and V_(RECT) _(_) _(HIGH) margin may be oneof the major factors in determining the dominant PRU.

As a method for controlling wireless charging power, V_(RECT) _(_)_(MIN) _(_) _(ERROR) is proposed for adjusting the output power of thePTU such that V_(RECT), which is registered as a current dynamicparameter, approaches V_(RECT) _(_) _(SET) _(_) _(STATIC) value receivedthrough a static parameter or V_(RECT) _(_) _(SET) _(_) _(DYNAMIC) valuereceived through a dynamic parameter, from the PRU.

Meanwhile, in a multi-charging case where the PTU charges two or morePRUs at the same time, one of the plurality of PRUs may be determined asthe dominant PRU, and transmission power or Itx may be adjusted suchthat the current associated with V_(RECT) of the determined dominant PRUapproaches a V_(RECT) _(_) _(SET) value. That is,E_(VRECT)=V_(RECT)−V_(RECT) _(_) _(SET) can be adjusted to be minimal.

Among methods for setting a dominant PRU, there is a method fordetermining a PRU having the highest utilization rate (for example, aPRU having the maximum P_(RECT)/P_(RECT) _(_) _(MAX)) as a dominant PRU.

Here, V_(RECT) _(_) _(SET) may be set as the most appropriate voltagefor the operation or charging of the PRU, and when there is a PRU whichis not determined as the dominant PRU, or V_(RECT) becomes too high, aheating problem may occur according to a coupling position or a matchingstate.

Hereinafter, a method for determining a dominant PRU according tovarious embodiments of the present disclosure will be described.

A PRU having the highest heat generation rate may be determined as adominant PRU, from among a plurality of PRUs that receive charging powerfrom a wireless power transmitting unit.

For example, information on the available maximum temperature (T_(MAX))of the PRU may be transmitted to the PTU through a PRU static signaltransmitted from the PRU. In addition, information on the temperature ofthe current PRU may be transmitted to the PTU through a PRU operationsignal transmitted from the PRU.

The PTU may calculate a heat generation rate, using information on theavailable maximum temperature and information on the current temperaturereceived from the PRU. The heat generation rate (T ratio) can becalculated using Equation 1 as follows.

$\begin{matrix}{{T\;{ratio}} = \frac{{current}\mspace{14mu}{temperature}\mspace{14mu}{of}\mspace{14mu}{PRU}}{T\;\max\mspace{14mu}{of}\mspace{14mu}{PRU}}} & (1)\end{matrix}$

For example, since OTP is most likely to occur in a PRU which has thesmallest current temperature state ratio of the wireless chargingreceiving unit, a wireless charging receiving unit having the smallestheat generation rate may be determined as the dominant PRU.

In determining the dominant PRU, when a PRU having the highest heatgeneration rate becomes the dominant PRU and the PTU matches the levelof transmission power to the standard of the dominant PRU, the PRUcloses the optimum V_(RECT) to reduce the heat generation. Accordingly,since a PRU having the highest heat generation rate is determined as thedominant PRU, the heat generation can be more efficiently managed.

FIG. 12 is a flowchart a processing method of a wireless powertransmitting unit, according to an embodiment of the present disclosure.Referring to FIG. 12, a PTUPTU may receive the PRU static signal at step1202 from the PRU, which is set to operate in the low-power mode at step1201. The PRU static signal may include the available maximumtemperature (T_(MAX)) of the corresponding PRU as shown in Table 5.

TABLE 5 Field Octets Description Use Units Optional fields validity 1Defines which optional fields Mandatory are populated Protocol Revision1 A4WP Supported Revision Mandatory RFU 1 Undefined N/A PRU Category 1Category of PRU Mandatory PRU Information 1 Capabilities of PRUMandatory (bit field) Hardware rev 1 Revision of the PRU HW MandatoryFirmware rev 1 Revision of the PRU SW Mandatory P_(RECT) _(—) _(MAX) 1P_(RECT) _(—) _(MAX) of PRU Mandatory mW × 100 V_(RECT) _(—) _(MIN) _(—)_(STATIC) 2 V_(RECT) _(—) _(MIN) (static, first estimate) Mandatory mVV_(RECT) _(—) _(HIGH) _(—) _(STATIC) 2 V_(RECT) _(—) _(HIGH) (static,first Mandatory mV estimate) V_(RECT) _(—) _(SET) 2 V_(RECT) _(—) _(SET)Mandatory mV Delta R1 value 2 Delta R1 caused by PRU Optional 0.01 ohmsTmax 1 Maximum temperature of PRU Mandatory Degrees Celsius (from −40°C.) RFU 4 Undefined N/A

The PTU that has received the available maximum temperature from the PRUmay store the available maximum temperature of each PRU at step 1203.

The PTU, enters the power transmission mode at step 1204, PTU andreceives a PRU dynamic signal from each of the plurality of PRUs beingcharged at step 1205. The PRU dynamic signal received from each PRU mayinclude information on the current temperature of the corresponding PRU,as shown in Table 6.

TABLE 6 Field Octets Description Use Units Optional fields validity 1Defines which optional fields are Mandatory populated V_(RECT) 2 DCvoltage at the output of the rectifier Mandatory mV I_(RECT) 2 DCcurrent at the output of the rectifier Mandatory mA V_(OUT) 2 Voltage atcharge/battery port Optional mV I_(OUT) 2 Current at charge/battery portOptional mA Temperature 1 Temperature of PRU Mandatory Degrees Celsius(from −40° C.) V_(RECT) _(—) _(MIN) _(—) _(DYN) 2 The current dynamicminimum rectifier Optional mV voltage desired V_(RECT) _(—) _(SET) _(—)_(DYN) 2 Desired V_(RECT) Optional mV (dynamic value) V_(RECT) _(—)_(HIGH) _(—) _(DYN) 2 The current dynamic maximum rectifier Optional mVvoltage desired PRU alert 1 Warnings Mandatory Bit field Tester Command1 PTU Test Mode Command Optional Bit field RFU 2 Undefined

The PTU may calculate the heat generation rate for each PRU based on thereceived available maximum temperature and the current temperature atstep 1207. The heat generation rate can be calculated using Equation 1described above.

Next, the PTU may determine the dominant PRU based on the calculatedheat generation rate, at step 1208. For example, the PRU having thehighest calculated heat generation rate can be determined as thedominant PRU). As described above, the heat generation can be moreefficiently managed by switching the dominant PRU to a power wirelessreceiving unit having the highest heat generation rate. The PTU mayadjust transmission power or Itx such that V_(RECT) of the determineddominant PRU closes to V_(RECT) _(_) _(SET).

FIG. 13 is a flowchart of a processing method of a PRU, according to anembodiment of the present disclosure. Referring to FIG. 13, the PRU isset to operate in the low-power mode at step 1301, and an availablemaximum temperature (T_(MAX)) of the PRU is added to a PRU static signalat step 1302. The PRU static signal to which the available maximumtemperature is added is transmitted to the PTU at step 1303).

With the PRU in the power transmission mode at step 1304, in which thePRU is being charged, the PRU may sense the current temperature by thetemperature sensor and the like at step 1305. The sensed currenttemperature may be included in the PRU dynamic signal and thentransmitted to the PTU at step 1306.

When not informing the PTU by separately adding the maximum value of thePRU temperature and the current temperature to the PRU dynamic signal orPRU static signal as described above, the PRU may calculate the heatgeneration rate and inform the same to the PTU. For example, the PRU maycalculate a heat generation rate (Tratio) from the maximum value(T_(MAX)) of the PRU temperature and the measured current temperature,using the above-described Equation 1, and transmit the calculated ratioto the PTU. The heat generation rate (Tratio) may be added to the PRUdynamic signal and then transmitted, as shown in Table 7.

TABLE 7 Field Octets Description Use Units Optional fields validity 1Defines which optional fields are Mandatory populated V_(RECT) 2 DCvoltage at the output of the rectifier Mandatory mV I_(RECT) 2 DCcurrent at the output of the rectifier Mandatory mA V_(OUT) 2 Voltage atcharge/battery port Optional mV I_(OUT) 2 Current at charge/battery portOptional mA Tratio 1 Temperature ratio of PRU Optional Bit field(Tcurrent_temp/Totp_threshold) V_(RECT) _(—) _(MIN) _(—) _(DYN) 2 Thecurrent dynamic minimum rectifier Optional mV voltage desired V_(RECT)_(—) _(SET) _(—) _(DYN) 2 Desired V_(RECT) Optional mV (dynamic value)V_(RECT) _(—) _(HIGH) _(—) _(DYN) 2 The current dynamic maximumrectifier Optional mV voltage desired PRU alert 1 Warnings Mandatory Bitfield Tester Command 1 PTU Test Mode Command Optional Bit field RFU 2Undefined

In Table 7, Tratio may be defined by a ratio of temperature ofTcurrent_temp/Totp_threshold, the Tcurrent temp refers to a currentlymeasured temperature, and the Totp_threshold refers to over-temperatureprotection threshold of PRU.

A PRU having the highest V_(RECT) ratio may be determined as thedominant PRU.

A PRU having the smallest ratio between V_(RECT) _(_) _(HIGH) _(_)_(STATIC) of the corresponding PRU included in the PRU static signal orV_(RECT) _(_) _(HIGH) _(_) _(DYN) of the corresponding PRU included inthe PRU dynamic signal, which are transmitted from the PRU, and V_(RECT)of the current PRU has the highest possibility to generate heat orexceed V_(HIGH). Therefore, the PRU satisfying the above condition maybe determined as the dominant PRU.

For example, the ratio of a voltage at a rectifier stage of the PRU maybe calculated using Equation 2 as follows.

$\begin{matrix}{{V\;{{ratio}( {V_{RECT}\mspace{14mu}{ratio}} )}} = \frac{V_{RECT}}{V_{RECT\_ HIGH}}} & (2)\end{matrix}$

The V_(RECT) _(_) _(HIGH) is a voltage value measured at a back end ofthe rectifier, and refers to a maximum voltage value when operatingwithin the optimum voltage range and may also be set to the V_(RECT)_(_) _(HIGH) _(_) _(STATIC) included in the PRU static signaltransmitted from the PRU, and it may be set to the V_(RECT) _(_) _(HIGH)_(_) _(DYN) included in the PRU operation signal transmitted from thePRU.

A PRU having the highest voltage ratio may be determined as the dominantPRU, among a plurality of the PRUs.

Thus, when the PRU having a high difference ratio of the V_(RECT) is setas a dominant PRU and then a transmission power level of the PTU isadjusted, the determined dominant PRU may close the optimum V_(RECT) toreduce the heat generation, and since it is not likely to exceed theV_(RECT) _(_) _(HIGH), a charging operation of the optimum range can beprovided.

FIG. 14 is a flowchart illustrating a processing procedure of a PTU,according to an embodiment of the present disclosure. Referring to FIG.14, a PTU, which is set to operate in a low-power mode at step 1401, mayreceive the PRU static signal from the PRU at step 1402. The PRU staticsignal may include maximum voltage value (V_(RECT) _(_) _(HIGH) _(_)_(STATIC)) information of a back end of the rectifier of thecorresponding PRU as shown in Table 8 below.

TABLE 8 Field Octets Description Use Units Optional fields validity 1Defines which optional fields Mandatory are populated Protocol Revision1 A4WP Supported Revision Mandatory RFU 1 Undefined N/A PRU Category 1Category of PRU Mandatory PRU Information 1 Capabilities of PRUMandatory (bit field) Hardware rev 1 Revision of the PRU HW MandatoryFirmware rev 1 Revision of the PRU SW Mandatory P_(RECT) _(—) _(MAX) 1P_(RECT) _(—) _(MAX) of PRU Mandatory mW × 100 V_(RECT) _(—) _(MIN) _(—)_(STATIC) 2 V_(RECT) _(—) _(MIN) (static, first estimate) Mandatory mVV_(RECT) _(—) _(HIGH) _(—) _(STATIC) 2 V_(RECT) _(—) _(HIGH) (static,first Mandatory mV estimate) V_(RECT) _(—) _(SET) 2 V_(RECT) _(—) _(SET)Mandatory mV Delta R1 value 2 Delta R1 caused by PRU Optional 0.01 ohmsTmax 1 Maximum temperature of PRU Mandatory Degrees Celsius (from −40°C.) RFU 4 Undefined N/A

As described above, the PTU that has received the maximum voltage valueinformation from the PRU may store the maximum voltage value informationof each PRU at step 1403.

With the PTU set in a power transmission mode at step 1404, the PTU mayreceive the PRU dynamic signal from each of the plurality of PRUs beingcharged at step 1405. The PRU dynamic signal received from each PRU mayinclude voltage (V_(RECT)) information of a back end of the rectifier ofthe corresponding PRU, as shown in Table 9.

TABLE 9 Field Octets Description Use Units Optional fields validity 1Defines which optional fields are Mandatory populated V_(RECT) 2 DCvoltage at the output of the rectifier Mandatory mV I_(RECT) 2 DCcurrent at the output of the rectifier Mandatory mA V_(OUT) 2 Voltage atcharge/battery port Optional mV I_(OUT) 2 Current at charge/battery portOptional mA Temperature 1 Temperature of PRU Mandatory Degrees Celsius(from −40° C.) V_(RECT) _(—) _(MIN) _(—) _(DYN) 2 The current dynamicminimum rectifier Optional mV voltage desired V_(RECT) _(—) _(SET) _(—)_(DYN) 2 Desired V_(RECT) Optional mV (dynamic value) V_(RECT) _(—)_(HIGH) _(—) _(DYN) 2 The current dynamic maximum rectifier Optional mVvoltage desired PRU alert 1 Warnings Mandatory Bit field Tester Command1 PTU Test Mode Command Optional Bit field RFU 2 Undefined

The PTU may check the received maximum voltage value information andcurrent voltage information at step 1406 and calculate a voltage ratiofor each PRU, based on the checked information at step 1407. The voltageratio may be calculated using Equation 2.

Next, the PTU may determine the dominant PRU based on the calculatedvoltage ratio at step 1408. For example, the PRU having the highestcalculated voltage ratio may be determined as the dominant PRU.

As described above, when the PRU having the highest voltage ratio is setas the dominant PRU and then a transmission power level of the PTU isadjusted, the dominant PRU may close the optimum V_(RECT) to reduce theheat generation. The PTU may adjust the transmission power or Itx suchthat V_(RECT) of the determined PRU closes to V_(RECT) _(_) _(SET).

FIG. 15 is a flowchart of a processing method of a PRU, according to anembodiment of the present disclosure. Referring to FIG. 15, with the PRUoperating in the low-power mode at step 1501, maximum voltage value(V_(RECT) _(_) _(HIGH) _(_) _(STATIC)) information of a back end of arectifier of the PRU may be added to the PRU static signal and then thePRU static signal may be transmitted at step 1502.

In the power transmission mode at step 1503, in which the PRU is beingcharged, the PRU may sense the V_(RECT) at step 1504. The sensedV_(RECT) information may be included in the PRU dynamic signal and thentransmitted to the PTU at step 1505.

In determining the dominant PRU as described above, it is important toguarantee the predictability of PTU operation. In addition, it isimportant to guarantee that the dominant PRU is not continuously changedby a result selection mechanism due to a different selection criteriathat is applied each time new information is provided to the PTU by thedynamic signal (for example, PRU dynamic signal).

For example, as the worst case, the dominant PRU may be changed at every250 ms. Accordingly, in order to solve such a problem, variousalgorithms to be described below may also be considered.

When the PTU is paired with the plurality of the PRUs, the dominant PRUcan be selected as a main PRU, by the PTU, for the optimum closed-looppower control algorithm.

The PTU may select any one of a V_(RECT) _(_) _(MIN) _(_) _(ERROR)algorithm or a η_(MAX) algorithm, as described above. In addition, thePTU may switch two algorithms and then apply the switched algorithms.However, the PTU is not configured to adjust (I_(TX) _(_) _(COIL)) sothat any PRU do not deviate beyond an optimal voltage area. Taking thisinto account, a preferred algorithm for the dominant PRU can be selectedby considering whether OVP (Over Voltage Protection) indication orV_(RECT) that is reported by the PRU is greater than V_(RECT) _(_)_(HIGH) or less than V_(RECT) _(_) _(MIN).

For example, when a PTU is paired with one PRU, the PTU may adjustE_(VRECT)=|V_(RECT)−V_(RECT) _(_) _(SET)| to be minimal. If the PTU ispaired with the plurality of PRUs, the PTU may adjust (I_(TX) _(_)_(COIL)) to minimize E_(VRECT) for the dominant PRU.

Hereinafter, various embodiments in which a PTU selects a dominant PRUwhen the PTU is to be paired with the plurality of the PRUs will bedescribed. The PTU may change (switch) the dominant PRU selectionmechanism, it may prove advantageous not to use a plurality ofmechanisms at the same time. When the PTU switches a mechanism forselecting the dominant PRU, the selected mechanism can be continued fora predetermined time (e.g., 5 seconds) by considering an exceptionalsituation which will be described below.

If the PTU selects a dominant PRU by using an algorithm that isdifferent from the current maximum Tratio algorithm, and detects a PRUsatisfying a Tratio>Temp threshold condition before a predetermined time(e.g., 5 seconds) interval is elapsed from last switching to a newdominant PRU selection mechanism, the PTU may immediately switch to aTratio mechanism for selecting the dominant PRU after detecting thecondition.

Hereinafter, examples of various mechanisms for selecting the dominantPRU will be described.

When the PTU selects the highest percentage utilization mechanism forthe selection of the dominant PRU, the PTU may select the dominant PRUhaving the highest percentage utilization compared to a rated output.The ratio of the rated output may be represented by Equation 3 asfollows.

$\begin{matrix}{{P\;{{ratio}( {P_{RECT}\mspace{14mu}{ratio}} )}} = \frac{P_{RECT}}{P_{RECT\_ MAX}}} & (3)\end{matrix}$

In Equation 3, P_(RECT) _(_) _(MAX) refers to the maximum output powerof the PRU design. The P_(RECT) _(_) _(MAX) may be transmitted to thePTU by the PRU static signal.

When the PTU selects the maximum temperature ratio (Tratio) mechanismfor the selection of the dominant PRU, the PTU may select a PRU havingthe maximum Tratio as the dominant PRU. The Tratio may be calculated bydividing Tcurrent reported as the PRU dynamic signal into Topt reportedas the PRU static signal. When the Tratio of the PRU exceeds apredetermined threshold (T_(threshold)), the PRU may switch the dominantPRU to another PRU. The PTU may use the predetermined threshold((T_(threshold))) greater than or equal to 0.75.

When the PTU selects a maximum V_(RECT) _(_) _(HIGH) ratio algorithm forthe selection of the dominant PRU, the PTU may select a PRU having thehighest V_(RECT) _(_) _(HIGH) _(_) _(RATIO) as the dominant PRU. TheV_(RECT) _(_) _(HIGH) ratio may be calculated by dividing V_(RECT) thatis reported as the PRU dynamic signal into V_(RECT) _(_) _(HIGH) _(_)_(STATIC) or V_(RECT) _(_) _(HIGH) _(_) _(DYN).

When the V_(RECT) _(_) _(HIGH) _(_) _(DYN) is reported to the PTU, theV_(RECT) _(_) _(HIGH) _(_) _(DYN) may be used instead of V_(RECT) _(_)_(HIGH) _(_) _(STATIC). When the V_(RECT) _(_) _(HIGH) ratio exceeds athreshold of V_(RECT) _(_) _(HIGH), the PTU may switch the dominant PRUto another PRU. The PTU may use the threshold of V_(RECT) _(_) _(HIGH)greater than or equal to 0.75

When the PTU selects the maximum V_(RECT) _(_) _(MIN) ratio algorithmfor the selection of the dominant PRU, the PTU may select a PRU havingthe highest V_(RECT) _(_) _(MIN) _(_) _(RATIO) as the dominant PRU. TheV_(RECT) _(_) _(MIN) _(_) _(RATIO) may be calculated by dividingV_(RECT) _(_) _(MIN) _(_) _(STATIC) or V_(RECT) _(_) _(MIN) _(_) _(DYN)into V_(RECT) that is reported as the PRU dynamic signal.

When the V_(RECT) _(_) _(MIN) _(_) _(DYN) is reported to the PTU, theV_(RECT) _(_) _(MIN) _(_) _(DYN) may be used instead of V_(RECT) _(_)_(MIN) _(_) _(STATIC). When the V_(RECT) _(_) _(MIN) ratio exceeds athreshold of V_(RECT) _(_) _(MIN), the PTU may switch the dominant PRUto another PRU. The PTU may use the threshold of V_(RECT) _(_) _(MIN)greater than or equal to 0.75.

In order to implement the algorithm described above, the PRU staticsignal may be configured as Table 10 below.

TABLE 10 Field Octets Description Use Units Optional fields validity 1Defines which optional fields Mandatory are populated Protocol Revision1 A4WP Supported Revision Mandatory RFU 1 Undefined N/A PRU Category 1Category of PRU Mandatory PRU Information 1 Capabilities of PRUMandatory (bit field) Hardware rev 1 Revision of the PRU HW MandatoryFirmware rev 1 Revision of the PRU SW Mandatory P_(RECT) _(—) _(MAX) 1P_(RECT) _(—) _(MAX) of PRU Mandatory mW × 100 V_(RECT) _(—) _(MIN) _(—)_(STATIC) 2 V_(RECT) _(—) _(MIN) (static, first estimate) Mandatory mVV_(RECT) _(—) _(HIGH) _(—) _(STATIC) 2 V_(RECT) _(—) _(HIGH) (static,first Mandatory mV estimate) V_(RECT) _(—) _(SET) 2 V_(RECT) _(—) _(SET)Mandatory mV Delta R1 value 2 Delta R1 caused by PRU Optional 0.01 ohmsTotp 1 Temperature threshold value Mandatory Bit field for overtemperature protection RFU 3 Undefined N/A

In Table 10, Totp may be an OTP threshold temperature and be configuredas shown in Table 11 below.

TABLE 11 Bit field Temperature ° C. 0-255 −40 to +215

In addition, in order to implement the algorithm described above, thePRU dynamic signal may be configured as Table 12 below.

TABLE 12 Field Octets Description Use Units Optional fields validity 1Defines which optional fields are Mandatory populated V_(RECT) 2 DCvoltage at the output of the rectifier Mandatory mV I_(RECT) 2 DCcurrent at the output of the rectifier Mandatory mA V_(OUT) 2 Voltage atcharge/battery port Optional mV I_(OUT) 2 Current at charge/battery portOptional mA Tcurrent 1 Temperature of PRU Optional Bit field V_(RECT)_(—) _(MIN) _(—) _(DYN) 2 The current dynamic minimum rectifier OptionalmV voltage desired V_(RECT) _(—) _(SET) _(—) _(DYN) 2 Desired V_(RECT)Optional mV (dynamic value) V_(RECT) _(—) _(HIGH) _(—) _(DYN) 2 Thecurrent dynamic maximum rectifier Optional mV voltage desired PRU alert1 Warnings Mandatory Bit field Tester Command 1 PTU Test Mode CommandOptional Bit field RFU 2 Undefined

In Table 12, Tcurrent may be a current temperature measured at the PRUand be configured as shown in Table 13 below.

TABLE 13 Bit field Temperature ° C. 0-255 −40 to +215

The present disclosure provides a method and apparatus that canefficiently control wireless charging power for the plurality of PRUs byapplying at least one algorithm of the above-described algorithm.

For example, a V_(RECT) of a PRU may be prevented from beingover-voltage condition (e.g., V_(RECT)>V_(RECT) _(_) _(MAX)). Inaddition, V_(RECT) of the PRU can be reduced to become a state ofV_(RECT)≤V_(RECT) _(_) _(HIGH) within a predetermined time (e.g., 5seconds) after reporting a state of V_(RECT)>V_(RECT) _(_) _(HIGH) bythe PRU. In addition, if the above conditions are satisfied, it can beguaranteed that V_(RECT) voltage for all PRUs is greater than V_(RECT)_(_) _(MIN) and smaller than V_(RECT) _(_) _(HIGH). In addition, if theabove conditions are satisfied, I_(TX) _(_) _(COIL) can be controlled tooptimize the V_(RECT) of PRU or to maximize the efficiency of a totalsystem.

While the present disclosure has been shown and described with referenceto certain embodiments thereof, it should be understood by those skilledin the art that many variations and modifications of the method andapparatus described herein will still fall within the spirit and scopeof the present disclosure as defined in the appended claims and theirequivalents.

What is claimed is:
 1. A method for transmitting wireless power in awireless charging system, the method comprising: receiving informationrelated to a temperature from each of a plurality of power receivingunits (PRUs); identifying a temperature ratio of each of the pluralityof PRUs based on the received information, wherein the temperature ratiois a current temperature relative to an available maximum temperature;determining a PRU from among the plurality of PRUs based on theidentified temperature ratio; and adjusting transmission power accordingto a voltage setting value of the determined PRU.
 2. The method of claim1, wherein the determined PRU is regarded as a dominant PRU.
 3. Themethod of claim 1, wherein the determined PRU is a PRU having thehighest temperature ratio from among the plurality of the PRUs.
 4. Themethod of claim 1, wherein the information related to the temperature istransmitted through a PRU dynamic signal that is transmitted by the PRUin a low power mode.
 5. The method of claim 1, wherein the informationrelated to the temperature is transmitted through a PRU dynamic signalthat is transmitted by the PRU in a power transmission mode.
 6. Awireless power transmitting unit (PTU), comprising: a communication unitconfigured to receive information related to a temperature from each ofa plurality of power receiving units (PRUs); a processor configured toidentify a temperature ratio of each of the plurality of PRUs based onthe received information, and determine a PRU from among the pluralityof PRUs based on the identified temperature ratio, wherein thetemperature ratio is a current temperature relative to an availablemaximum temperature; and a power transmitter configured to transmitpower to the plurality of PRUs based on a voltage setting value of thedetermined PRU.
 7. The PTU of claim 6, wherein the processor adjuststransmission power of the power transmitter according to the voltagesetting value of the determined PRU.
 8. The PTU of claim 6, wherein theinformation related to the temperature is transmitted through PRUdynamic signal that is transmitted by the PRU in a low power mode. 9.The PTU of claim 6, wherein the information related to the temperatureis transmitted through a PRU dynamic signal which is transmitted by thePRU in a power transmission mode.
 10. The PTU of claim 6, wherein thedetermined PRU is regarded as a dominant PRU.
 11. The PTU of claim 6,wherein the determined PRU is a PRU having the highest temperature ratiofrom among the plurality of the PRUs.